1. Field of the Invention
The present invention relates to devices for the spine and, more particularly, to a spinal implant for the treatment of stenotic spinal bone.
2. Background Information
As we age various changes can occur in the body. For instance, the ligaments of the spine can thicken and calcify (i.e. harden from deposits of calcium), bone and joints may enlarge, bone spurs called osteophytes may form, spinal discs may collapse and bulge (i.e. herniate) or one vertebra may slip over another (spondylolisthesis). Any one or these conditions and/or others can cause what is known as lumbar spinal stenosis. Lumbar spinal stenosis is a narrowing of the bony spinal canal. While some people are born with this condition, most often spinal stenosis is the result of one of the above-identified degenerative conditions that develop in mainly the middle-aged and elderly population.
In this regard, spinal stenosis may be considered as the gradual result of aging and “wear and tear” on the spine from everyday activities. Such degenerative or age-related changes in our bodies can lead to compression of nerves (i.e. pressure on the nerves that can cause pain and/or damage). Symptoms of lumbar spinal stenosis include leg pain (“pins and needles”) that can limit standing, walking, self-supporting daily activities, work, social and recreational pursuits. Lack of activity because of lumbar spinal stenosis may lead to obesity, depression and general physical deterioration.
Once diagnosed with lumbar spinal stenosis the doctor will usually try non-surgical treatments first. Such treatments may include anti-inflammatory medications (orally or by injection) to reduce associated swelling or analgesic drugs to control pain. Physical therapy may be prescribed with goals of improving ones strength, endurance and flexibility so that you can maintain or resume a more normal lifestyle. Spinal injections such as an epidural injection of cortisone may also be used. Such non-surgical treatments do not correct the spinal canal narrowing of lumbar spinal stenosis itself but may provide long-lasting pain control and improved life function without requiring a more invasive treatment. However, as a last resort for those patients who don't respond to non-surgical treatments, surgery will be advised.
Lumbar spinal stenosis is the most common reason for back surgery in people over the age of 50 in the United States. While there are various non-surgical treatments for lumbar spinal stenosis, a surgical procedure known as a laminectomy may be performed in order to reduce or eliminate the symptoms of lumbar spinal stenosis. A laminectomy or lumbar decompression surgery has the goal of opening up the bony canal to improve available space for the spinal nerves. As indicated, however, a laminectomy is usually a last resort for treating lumbar spinal stenosis. This is because a laminectomy is an invasive surgical procedure.
Fortunately, another surgical treatment for lumbar spinal stenosis is known that is less invasive than a laminectomy. This other surgical treatment involves implanting a spinal spacer between bony projections of adjacent vertebrae, particularly, but not necessarily, between spinous processes of adjacent vertebrae. It can be appreciated that the more compact the spinal spacer, the less invasive the surgical implantation procedure.
In view of the foregoing, it is therefore desirable to provide a compact spinal spacer. Moreover, it is desirable to provide a spinal spacer that is compact during implantation and expandable in situ.